TW200823823A - Controlling apparatuses for controlling a plurality of LED strings and related light modules - Google Patents

Abstract

Controlling apparatuses for controlling a plurality of LED strings and related light modules are disclosed, wherein each of the LED strings has a first terminal being electrically connected to an operating voltage. One of the proposed controlling apparatuses includes: a plurality of transistors, each having a control terminal, a first terminal, and a second terminal, wherein the first terminal of each transistor is electrically connected to a second terminal of a corresponding string of the LED strings, and the second terminals of the plurality of transistors are respectively grounded through a plurality of impedance elements; and a transistor controller, electrically connected to the control terminals of the plurality of transistors, for controlling a current of the first terminal of each transistor by adjusting an input signal of the control terminal of the transistor according to a voltage of the second terminal of the transistor.

Description

200823823 IX. Description of the Invention: [Technical Field] The present invention relates to a technique for controlling a light-emitting diode, and more particularly to a control device for controlling a plurality of light-emitting diodes and a related light source module. [Prior Art] Applications using light-emitting diodes (LEDs) as light-emitting sources are becoming more and more popular. For example, a backlight module of a conventional liquid crystal display panel is mostly a cold cathode fluorescent lamp (CCFL) as a light source. Nowadays, with the increasing luminous efficiency and lower cost of light-emitting diodes, light-emitting diodes have gradually replaced cold cathode fluorescent tubes as a backlight module light source. In the prior art, a plurality of light emitting diodes are often connected in series to reduce the number of driving circuits required and reduce the total driving current of the light emitting diodes. However, due to variations in the process, it is difficult to ensure that all of the light-emitting diodes in different series have completely identical component parameters. In addition, environmental factors such as temperature may also affect the component parameters of the light-emitting diode. For example, the forward voltage (plus * W) of δ 'different light-emitting diodes is often slightly different from each other. The arrangement of a plurality of light-emitting diodes in a series will accumulate the voltage error of all the light-emitting diodes in the same-serial series, and the total forward voltages accumulated by the different light-emitting diodes. The error will usually vary. In this case, 'even if the same operating voltage is applied to different LED series, the current flowing through the individual LED series will be the total forward voltage accumulated by each LED series. The error varies and is different. As a result, the LED arrays will have different brightness due to current inconsistency. Therefore, when the light-emitting diode series is used as the light source of the backlight module of the liquid crystal display panel, the liquid crystal display panel often causes a color unevenness (Mura) due to uneven brightness of the backlight. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a control device and a related light source module that can control a plurality of corrections for the brightness of the == column to provide a control device for the polar body. Controlling a plurality of light-emitting diodes 2, wherein the plurality of light-emitting diodes are in a series - control, a first end and a second turn, and the gem is electrically connected to the two ends of the plurality of light-emitting diodes The second ends of the plurality of transistors are respectively grounded through the 200823823 ^ plurality of impedance elements; and a transistor controller electrically connected to the control ends of the plurality of transistors for using the second of each of the transistors The voltage of the terminal adjusts the input signal of the control terminal of the transistor to control the current of the first end of the transistor. The present invention further provides a light source module, comprising: a plurality of LED arrays, each having a first end and a second end, and the first ends of the plurality of LED arrays are Electrically connected to a working voltage; a plurality of transistors each having a control end, a first end and a second end, wherein the first end of each transistor is electrically connected to the plurality of light emitting diodes a second end of the plurality of transistors in the body string, and the second end of the plurality of transistors is grounded through the plurality of impedance elements respectively; an error calculation circuit electrically connected to the second of the plurality of transistors a terminal for respectively calculating a difference between a voltage of the second end of each transistor and a corresponding reference voltage; and a transistor controller electrically connected to the error calculation circuit and the 10 control terminals of the plurality of transistors, The current at the first end of each transistor is controlled in accordance with the calculation result of the error calculation circuit. [Embodiment] Please refer to FIG. 1 , which is a simplified schematic view of a light source module 100 according to an embodiment of the invention. The light source module 100 includes a plurality of LED arrays 110a to 110n, and a plurality of LEDs 200823823 serial control device 120 for controlling the plurality of LEDs. In this embodiment, the first ends of the LED arrays 110a to 11 On are electrically connected to an operating voltage vin, and the LED arrays 110a to 110η have the same number of same-color LEDs. . The control device 120 in the light source module 100 is for controlling the LED arrays 110a to 110n' so that the LED arrays u〇a to ii〇n can have substantially the same brightness. As shown in Fig. 1, the control device 1 includes a plurality of transistors 130a to 130n, an error calculation circuit 14A, a transistor_controller 150, and a plurality of impedance elements 160a to 160n. In a preferred embodiment, the impedance elements 160a-160n have substantially the same impedance value. For example, the impedance elements 160a-160n can each be implemented with a plurality of resistor elements having substantially the same resistance value. The operation of the control device 120 will be further described below. The transistors n〇a~130η in the control device 120 of the embodiment are all a bipolar junction transistor (BJT), and each transistor includes a control end, a first end and a Second end. In this embodiment, the control terminal is a base. The first end is a collector and the second end is an emitter. As shown in FIG. 1, the collectors of the transistors 130a to 130n are electrically connected to the second ends of the LED arrays 110a to 110n, respectively, and the emitters of the transistors 130a to 130n are respectively transmitted through the impedance elements 160a. ~160η grounded. In practice, the transistors 130a~13On should have substantially the same common-emitter current gain, and both operate in the active region (active 200823823 'region) to improve performance and reduce control complexity. However, the actual embodiment of the present invention is not limited thereto. As mentioned above, environmental factors such as process variation or temperature may cause the total forward voltage error accumulated by the LED series ll〇a~110η to be different, thereby causing a flow through the LED array 110a. The currents Icl and Ic2 to Icn of ~110η are inconsistent in size. In this embodiment, the control device 120 controls the currents Icl~Icn of the LED series 110a~110n by the transistors 13〇a~13〇n, respectively, so that the brightness of the LEDs is serially arranged. Can tend to be consistent. Specifically, the control device 120 uses the error calculation circuit 140 to calculate the difference between the emitter voltage VFi of each of the transistors 130a to 130n and a corresponding reference voltage Vref. Preferably, the error calculation circuit 140 can amplify the difference between the emitter voltage VFi of each transistor and the reference voltage Vref, and increase the resolution of the feedback signal by φ. In practice, error calculation circuit 140 can be implemented with one or more operational amplifiers. For example, the error calculation circuit 140 can be a single operational amplifier for sequentially calculating the difference between the emitter voltage of the transistors 130a to 130n and the reference voltage Vref. Alternatively, the error calculation circuit 140 may simultaneously calculate the difference between the emitter voltages of the transistors 130a to 130n and the reference voltage Vref in a parallel processing manner using a plurality of operational amplifiers. For example, the error calculation circuit 140 can use a first operational amplifier (not shown) to calculate the difference between the emitter voltage VF1 of the transistor 130a and the reference 200823823 'voltage Vref, and simultaneously utilize a second operational amplifier (Fig. Not shown) to calculate the difference between the emitter voltage of the transistor 130b and the reference voltage, wherein the first and second operational amplifiers preferably have substantially the same gain. The transistor controller 150 The base current Ibi of each of the transistors 130a to 130n is adjusted according to the calculation result of the error calculation circuit 140, so that the collector currents of the transistors 130a to 130n (that is, flowing through the light-emitting diode) The currents Icl to Icn of the series 110a to 110n can approach a predetermined value. The operation and implementation of the transistor controller 150 will be further described below in conjunction with FIG. FIG. 2 is a simplified schematic diagram of one embodiment of a transistor controller 150. Since the transistor controller 150 adjusts the base current and the collector φ current of the mother-transistor in the transistors 130 a to 13 On in the same manner and structure, only the transistor controller 150 adjusts the transistor 130a. An example of the base current Ib1 will be described. In addition, in the second figure, except for the transistor 101a and its corresponding LED array 110a and the impedance element 160a, other transistors, LED arrays, and impedance elements are omitted. As shown in FIG. 2, the transistor controller 150 of the present embodiment includes a voltage source 210 for outputting a predetermined voltage Vd. The variable resistor 220 is electrically connected to the voltage source 210 and the base of the transistor 130a. And a determining unit 230 electrically connected to the error calculating circuit 140 and the 12200823823 variable resistor 220 for changing the resistance value of the variable resistor 220 according to the calculation result of the error calculating circuit 140 to adjust the transistor The base current IM of 130a, when the transistor 130a is operated in the active region, the collector current Icl and the base current Ibl have the following linear relationship:

Icl = /3 X Ibl ( 1 ) where /5 is the common emitter current gain of transistor 130a. The operation of the error calculation circuit 140 for calculating the voltage difference Verl between the emitter voltage VF1 of the transistor 130a and the reference voltage Vref can be expressed by the following equation:

Veil - Ax ( Vref - VF1 ) (2) where A is the gain of the error calculation circuit 140. Assuming that the resistance value of the variable resistor 220 is R1, the relationship between R1 and the base current Ibl of the transistor 130a is as follows:

Ibl X Rl-Verl - (VF1 + Vbe) (3) where Vbe is the voltage across the base and emitter of transistor 130a. As known from 13 (4) 200823823 (3)

Ibl

Verl - (VFl + Vbe)

Rl can be obtained by substituting equation (2) into equation (4).

Ibl = + ~ R\ a + l) xVFl - Vbe — (5) Next, the following relation can be obtained by substituting equation (1) for human (5): icl . jsx^^LziA+ihm—sheng Rl (6) , , two K1 /5\8, 〖21><(eight+1), since the gain calculation circuit 1's gain eight is usually much larger than the b, K1 and K2 will be very close. Therefore, rewrite equation (6) as:

Icl

Rl Rl (7) 14 200823823 In the equation (7), ΚΙ, Vbe, and 々 are both fixed values. Therefore, the decision unit 23 of the transistor controller 150 can calculate the result Verl according to the error calculation circuit 14〇. The resistance value R1' of the variable resistor 22A is changed to adjust the base current Ib1 of the transistor 130a. Thus, the purpose of controlling the collector current Icl of the transistor 130a can be achieved. In the present embodiment, the determining unit 230 controls the transistor 13 such as the collector current ici to a predetermined value or a predetermined range by adjusting the resistance value of the variable resistor 22〇 [11]. Similarly, the transistor controller 15 can adjust the collector currents Ic2 to Icn of the other transistors 13〇b to 13〇n in the control device 120 by the same architecture. In this way, the currents Icl and Ic2 to Icn flowing through the LEDs n〇a to ii〇n tend to be uniform, so that the brightness of the LED arrays 110a to 110n can be greatly improved. Unequal situations. As can be seen from the above description, the light source module 1 前 used as the light source of the backlight module of the liquid 曰曰曰 display panel can effectively solve the color unevenness (Mura) phenomenon of the liquid crystal display panel. Although the light-emitting diodes included in each of the light-emitting diodes in the light source module 100 are light-emitting diodes of the same color, this is merely an embodiment and is not intended to limit the practical application scope of the present invention. In practice, the colors of the LED arrays 110a to 110n may be different from each other. For example, the LED strings 10a to 11b may include at least one string of the first color to be at least one string of 15 200823823 ' and a second color. In practice, the total forward voltage values of the LEDs of different colors may vary. Therefore, the error calculation circuit 140 can use different reference voltages to compare the feedback voltage VFi corresponding to the LED arrays of different colors. Alternatively, the determining unit 230 in the transistor controller 150 can respectively set different target current values for the LED arrays of different colors, and control the brightness of the individual LED arrays by using the feedback control method described above. which performed. In addition, some or all of the bipolar junction transistor (BJT) transistors 13 (^~13〇11) in the foregoing control device 120 may be replaced by a plurality of insulated gate bipolar transistors (IGBTs). And the insulating gate bipolar transistors preferably have substantially the same conductivity (Transconductance). For the insulated gate bipolar transistor, the control terminal is a gate, and the first end thereof The two ends are the same as the bipolar junction transistors, which are collector and emitter respectively. In this architecture, the error calculation circuit 140 calculates an error value according to the emitter voltage of each insulation gate bipolar transistor. The transistor controller 150 adjusts the gate input voltage of the insulating gate bipolar transistor according to the calculation result of the error calculating circuit 140 to control the collector current of the insulating gate bipolar transistor. For the preferred embodiment of the present invention, the equivalent changes and modifications made by the scope of the present invention should be within the scope of the present invention. 16 200823823 [Simple description of the drawing] 々 1st The light source module of the present invention - a simplified schematic view of the embodiment of Example 2 Di graph of the i-th transistor in FIG Control - Figures do not think the simplified embodiment of Tony known.

[Description of main component symbols] 100 light source modules 110a, 110b to 110n LED series 120 control devices 130a, 130b to 130n transistor 140 difference calculation circuit 150 transistor controllers 160a, 160b to 160n impedance element 210 voltage Source 220 variable resistor 230 decision unit 17

Claims (1)

200823823 " X. Application Patent Range: 1. A control device for controlling a plurality of LED arrays, wherein the first ends of the plurality of LED arrays are electrically connected to an operating voltage, The control device includes: a plurality of transistors, each having a control end, a first end and a second end, wherein the first end of each transistor is electrically connected to the plurality of LED arrays a second end of the plurality of transistors, wherein the second ends of the plurality of transistors are respectively grounded through the plurality of impedance elements; and a transistor controller electrically connected to the control ends of the plurality of transistors The input signal of the control terminal of the transistor is adjusted according to the voltage of the second end of each transistor to control the current of the first end of the transistor. 2. The control device of claim 1, further comprising an error calculation circuit electrically connected to the transistor controller and the second end of the plurality of transistors for calculating each power The difference between the voltage at the second end of the crystal and a corresponding reference voltage, wherein the transistor controller adjusts the input signal of the control terminal of the transistor according to the result of the nose of the error meter. 3. The control device of claim 2, wherein the error calculation circuit amplifies a voltage difference between a second end of each transistor and a voltage of the reference 18 200823823. 4 as described in claim 2 The control device, wherein the error calculation circuit comprises a first operational amplifier for respectively calculating a difference between a voltage of the second end of the plurality of transistors and the reference voltage. 5. The difference in pressure. The control device of claim 4, wherein the error calculation circuit further comprises - when the second (4) large n ' is calculated, the voltage of the second end of the second transistor is calculated and the reference current is 6. The control device of claim 5, wherein the second operational amplifier has substantially the same gain. 7. The control device of claim 1, wherein the plurality of transistors are bipolar transistors. 8. The transistor of item 7 of the scope of the patent application has substantially the same common emitter current gain as the phase of the device. 9. For example, the 7th body controller of the patent application model includes: the control device 'which causes the electro-plasma voltage source' to be used for wheeling-predetermined voltage. A variable resistor' electrical connection; Corresponding to the plurality of transistors 19 200823823 corresponding to the control end of the transistor; and, the unit is connected to the error calculation circuit and the variable circuit is used to change according to the calculation result of the error calculation circuit. I: a resistance of the resistance i' to adjust the input current of the control terminal of the corresponding transistor. 10. If you apply for a patent scope! The control device of the item, wherein the plurality of germanium crystals are insulated gate bipolar transistors. U. The control device of claim 10, wherein the plurality of transistors have substantially the same conductivity characteristics. The control device of claim 1, wherein the transistor controller adjusts an input voltage of a control terminal of each transistor according to a calculation result of the error calculation circuit to control a first end of the transistor. Current. 13. The control device of claim i, wherein the plurality of transistors comprises at least one bipolar junction transistor and at least one insulation gate bipolar transistor. 14. The control device of claim 1, wherein the plurality of impedance elements have substantially the same impedance value. The control device of claim 1, wherein the plurality of LED arrays comprise a first series corresponding to one of the first colors and corresponding A second string of one of the second colors. The control device of claim 1, wherein the plurality of transistors are operated in the active region. The control device of claim 1, wherein the control end is a base, the first end is a collector, and the second end is an emitter. A light source module includes: a plurality of LED arrays, each having a first end and a second end, wherein the first ends of the plurality of LED arrays are electrically connected to one The operating voltage; the plurality of transistors each have a control end, a first end and a second end, wherein the first end of each transistor is electrically connected to one of the plurality of LED strings Corresponding to the second end of the series, the second end of the plurality of transistors is respectively grounded through the impedance element; the error calculation circuit is electrically connected to the second end of the plurality of transistors for respectively calculating The voltage at the second end of each transistor: 21 200823823 a difference between the reference voltages; and a transistor controller electrically connected to the error calculation circuit and the control terminals of the plurality of transistors for The calculation of the error calculation circuit controls the current at the first end of each transistor. The light source module of claim 18, wherein the plurality of transistors are bipolar transistors. The light source module of claim 19, wherein the transistor controller adjusts an input current of a control terminal of each transistor according to a calculation result of the error calculation circuit to control a first end of the transistor Current. The light source module of claim 19, wherein the plurality of transistors have substantially the same common emitter current gain. The light source module of claim 18, wherein the plurality of transistors are insulated gate bipolar transistors. The light source module of claim 22, wherein the transistor controller adjusts an input voltage of a control terminal of each transistor according to a calculation result of the error calculation circuit to control a first end of the transistor Current. The light source module of claim 18, wherein the plurality of light emitting diode strings correspond to the same color. The light source module of claim 18, wherein the plurality of transistors are operated in the active area. & For example, the end of the light source module described in item 18 of the patent scope is the base, the total oxime and the working electrode. The younger brother is the collector' and the second end is the shot. twenty three